The thing about birthing a lamb on camera is you only get one take.

Saoirse Ronan had been getting up at dawn to observe local farmers in Orkney in action, soaking in as much as she could. But soon it was her turn. Not only would she have a life in her hands: She had to look like she’d been doing it her whole life. She was terrified.

It wouldn’t be the last time Ronan, 30, would have to step out of her comfort zone to make the “ The Outrun ” (in theaters Friday), a harrowing and transcendent portrait of addiction and recovery which she produced alongside her husband, actor Jack Lowden. She’d yell and scream and say the meanest things she could think of to her fellow actors. She’d go from euphoric to inconsolable on a dime in a chaotic, drunken haze. And she’d plough the despairing depths of a very sick person about to relapse.

But after 20 years of acting, these were challenges she was ready for. There’s a reason her performance, defining and distinctive on a resume full of memorable characters, from Briony Tallis to Lady Bird, has garnered comparisons to Gena Rowlands in “A Woman Under the Influence.”

It was Lowden who put Amy Liptrot’s bestselling memoir in her hands during the pandemic, thinking it might be an interesting role for her.